Vision plays an essential role during normal locomotion. Visual guidance is of particular clinical importance in elderly people, among whom decreased visual function is a major contributing factor to falls that often result in serious injury. The present proposal has two aims. The first is to explore the neural mechanisms underlying visual guidance during locomotion. The second is to investigate how visual information is transmitted to the motor system to guide locomotion. Cats are better suited than monkeys for this project because it is both feasible to record from single neurons in locomoting cats, and to do behavioral studies on unrestrained cats. Moreover, the areas of visual cortex most directly involved in visual guidance are similar in cats and monkeys.To explore how neurons in visual cortex analyze and transmit information during locomotion, electrodes will be placed in two key visual cortical areas. Responses will be recorded while cats walk down a long test alley, and the cat's gaze will also be monitored. We will correlate responses with several factors: the presence or absence of small objects cluttering the alley floor, the gaze behavior of the cat, and the direction selectivity of the neurons under study.To investigate the link between visual and motor systems during locomotion, the relay from visual cortex to cerebellum will be reversibly blocked in cats that are walking down a test alley. When the alley is cluttered, cats rely on vision to accurately place their feet. The hypothesis is that interruption of transmission of visual cortical information to cerebellum will cause a substantial increase in visually-guided stepping errors.